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Subject: Re: [OMPI users] MPI loop problem
From: Ralph Castain (rhc_at_[hidden])
Date: 2009-08-18 10:32:19

Sorry, but there is no way to answer this question with what is given. What
is "my_sub" doing? Which version of OpenMPI are you talking about, and on
what platform?

On Tue, Aug 18, 2009 at 8:28 AM, Julia He <springwater4he_at_[hidden]> wrote:

> Hi,
> I found that the subroutine call inside a loop did not return correct value
> after certain iterations. In order to simplify the problem, the inputs to
> the subroutine are chosen to be constant, so the output should be the same
> for every iteration on every computing node. It is a fortran program, after
> the initialization the program goes like this:
> do i = 1, N
> call my_sub(A, B, C, re)
> print *, mypn, A, B, C, re
> end do
> where re is the output value of the my_sub, A, B, C are inputs to my_sub.
> 570 is the number of correct iterations. If the combined instances does not
> exceed 570, the output is fine. For example, if I requested 10 computing
> nodes and N were 40, so it gives 10*40=400 instances, the output would be
> fine. But if the combined instances exceeded 570, the first 570 is fine, but
> the rest will return NaN value. For example, if the number of computing
> nodes were 20 and N were 40, which gives 20*40=800 instances, then the first
> 570 are fine, but the rest are NaN value.
> Does someone know what might cause the problem? I googled it, but can't
> find a clue where to start. Please also let me know what else you need to
> debug the problem.
> Thanks.
> Julia
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